Industrial-rated circuit breakers are currently available having operating components that are designed for automatic assembly to provide cost improvement as well as improved operating efficiency. The precision alignment performed by the automated assembly equipment assembles the operating components within very close operating tolerances. An operating mechanism designed for down-loaded automated assembly is described in U.S. Pat. No. 4,864,263. The operating mechanism assembly includes a pair of operating springs that are overcentered for rapidly driving the movable contact arm and the attached movable contact away from the stationary fixed contact to interrupt the circuit current. The operating mechanism includes a cradle operator which engages a latch assembly to prevent the movable contact arm from being driven to its open position under the urgence of the charged operating springs. The compact latch assembly includes a primary and secondary latch operating within a common support structure.
U.S. Pat. No. 3,671,890 entitled "Manually Operable Molded Case Circuit Breaker With Special Trip Testing Means" and U.S. Pat. No. 4,982,173 entitled "Rotatable Trip Test Assembly for Molded Case Circuit Breakers" both describe a trip-to-test button that allows the circuit breaker operating mechanism to be manually articulated for test purposes. In some applications, it is more advantageous to articulate the operating mechanism by linear displacement of the trip-to-test button shaft rather than by rotation.
U.S. Pat. No. 5,075,658 entitled "Molded Case Circuit Breaker Trip-To-Test Button and Auxiliary Switch Interface" describes one such trip-to-test button having an extended shaft for interacting with the circuit breaker operating mechanism that is automatically assembled during the circuit breaker manufacturing process.
When such trip-to-test buttons are used within higher ampere rated applications in accordance with European Electrical Industry Standards, the arc gases generated within the circuit breaker enclosure when such breakers are tested under full load conditions contact the bottom parts of the trip-to-test buttons that interact with the circuit breaker operating mechanism. The accumulation of the associated debris that accompanies the arc gases could interfere with future trip-to-test functions.
One purpose of the invention, accordingly, is to provide a trip-to-test button assembly that is automatically assembled and integrally protected against arc gas debris contamination.